The present invention relates to an injection apparatus for injecting a molten metal into a die cavity.
Injection molding machines such as die casting machines are classified into a vertical casting type in which a molten metal is injected upward into a die cavity and a horizontal casting type in which a molten metal is laterally injected into a cavity. Of these two types, the vertical casting type is generally constituted as follows. That is, an injection frame supported by a machine base is suspended in a pit beneath a floor provided under metal molds. An entire injection apparatus is supported by the injection frame so as to be set upright or tilted. This injection apparatus includes an injection cylinder connected to a hydraulic device, an injection sleeve supported concentrically with the injection cylinder by a vertically movable sleeve frame at the injection cylinder side, and a plunger coupled to a piston rod of the injection cylinder via a coupling and having a plunger tip at its distal end which is inserted to be movable forward/backward in an inner hole of the injection sleeve. The injection sleeve of the injection apparatus is tilted by a tilting cylinder, and a molten metal is teemed therein. The injection cylinder is then raised by the tilting cylinder, moved upward together with the sleeve frame by an elevating cylinder, and connected to a stationary sleeve at the metal mold side. Thereafter, when an oil is supplied to the injection cylinder, the plunger is moved upward together with the piston rod, and the molten metal in the injection sleeve is pushed by the plunger tip and injected into the die cavity via the stationary sleeve. After the molten metal is solidified, a cast product is obtained. Vertical die casting machines of this type are disclosed in, e.g., U.S. Pat. Nos. 4,088,178, 2,454,961 and 4,655,274.
In such a conventional injection apparatus, however, an injection cylinder is hydraulically activated. Therefore, since the entire apparatus is large in size, a large installation space including conduits is required, and its controllability is degraded.